1. Field of the Invention
The present invention relates to an antenna, and more particularly to a coupling antenna that has a substrate, a first coupling member, a second coupling member and an inducting conductor so that the coupling antenna has a wide bandwidth and a small size.
2. Description of Related Art
Wireless telecommunication technologies have greatly developed to be mature, reliable and marketable so that the market demand for the wireless products greatly increases in the recent years.
With reference to FIG. 1, U.S. Pat. No. 6,081,242 discloses an “antenna matching circuit” that has a printed circuit board (PCB) (24a), a connection pad (40), a first inductor (34), a second inductor (38) and a ground plane (42). The PCB (24a) has a top surface. The connection pad (40) is mounted on the top surface of the PCB (24a). The first inductor (34) is zigzag, is mounted on the PCB (24a), is coupled to the connection pad (24a) and has an inside end. The second inductor (38) is zigzag, is mounted on the top surface of the PCB (24a) and has an inside end. The inside ends of the first and second inductors (34, 38) cooperate to form a capacitor (26a). The ground plane (42) is mounted on the top surface of the PCB (24a) and is coupled to the second inductor (38). The zigzag first and second inductors (34, 38) improve the inductance effect and the electronic coupling efficiency and reduce the size of the antenna to achieve multi-band operation. However, an area of the antenna generating capacitive coupling effect is small. Therefore, the operating bandwidth of the antenna is narrow so that the practical application of the antenna is limited.
To overcome the shortcomings, the present invention provides a coupling antenna to mitigate or obviate the aforementioned problems.